This invention relates to an amplifier consisting of MOSFETs (insulated gate field effect transistors) and to a technique which is effective when used, for example, for a main amplifier for amplifying a read-out signal from a memory array in a dynamic type RAM (random access memory).
The inventor of the present invention developed previously an MOS amplifier such as shown in FIG. 1 which constitutes a main amplifier in a dynamic type RAM. This MOS amplifier consists of two sets of MOS differential amplifiers, and is arranged to receive complementary input signals in mutually opposite phases and to produce complementary output signals from the respective output terminals. A MOS amplifier similar to the arrangement of FIG. 1 is shown in FIG. 6 of U.S. Pat. No. 4,509,147 issued on Apr. 2, 1985, which patent is hereby incorporated by reference.
Although the circuit of FIG. 1 is useful as a main amplifier, the inventor of the present invention determined that it would be desirable to improve its sensitivity. Regarding the structure of the dynamic type RAMs, it is noted that Japanese Laid-Open No. No. 57-082282 is an example of a prior art reference that describes in detail the dynamic type RAM.